border-1px-bottom($color){
  position: relative
  &::after{
    display: block
    position: absolute
    left:0
    bottom: 0
    width:100%
    border-top:1px solid $color
    content:''
  }
}

border-1px-top($color){
  position: relative
  //实验作用，写一个上边框1px的
  &::after{
    display: block
    position: absolute
    left:0
    top: 0
    width:100%
    border-top:1px solid $color
    content:''
  }
}
border-1px-right($color){
  position: relative
  &::after{
    display: block
    position: absolute
    right:0
    top: 0
    height:100%
    border-right:1px solid $color
    content:''
  }
}
border-1px-left($color){
  position: relative
  &::after{
    display: block
    position: absolute
    left:0
    top: 0
    height:100%
    border-left:1px solid $color
    content:''
  }
}

border-none(){
  &::after{
    display:none
  }
}


bg-image($url){
  background-image:url($url+"@2x.png")
  @media (-webkit-min-device-pixel-ratio:3),(min-device-pixel-ratio:3){
    background-image:url($url+"@3x.png")
  }
}